Well, assuming that your 1st preference is CS at Pilani. EEE at Pilani is arguably one of the most difficult branches out there. Based on the conversations I had with my friends from both the BITS campus, here is what I can tell you about the courses.

• You generally have to compete with the top students on the Campus. Also, the EEE course material is not everyone's cup of tea.
• The EEE placements are quite good, though not for everyone. There are more high pointers in EEE than in any other branch. Thus good companies prefer to hire from among those.
• Placements might be better for CS at Goa, though in some other respects you might sell yourself short with this choice.

So, if you want an easy life, better go for CS in Goa. Otherwise, choose EEE at Pilani.

NIT Surathkal IT is far superior to NIT Calicut. It is well-known in India for its CSE/IT branches. It is a highly regarded engineering college in India, and after four years of B.Tech college, the specific branch does not matter.

NITK outperforms Calicut in terms of reputation and placements. Furthermore, because of the higher cutoffs, the quality of students may be slightly higher here.

IT at NITK is nearly equivalent to CSE here. During placements, nearly all companies open to CS are open for IT as well.

The subjects taught and the syllabus in both departments are also similar. In fact, the IT department may be slightly better than the CS department in terms of facilities and infrastructure, as it is newer. Previously, the quality of students in CS was higher than in IT, but with significant increases in IT cutoffs, both are now equally good.

I know some of the people from both institutes. Based on what I heard from them, IIIT Bhopal is better than IIIT Ranchi. 

A few of the reasons to choose IIIT Bhopal are as follows. 

• Mentor Institute: IIIT Bhopal is mentored by NIT Bhopal and classes are held inside the campus of NIT Bhopal itself. So you will have access to all the experienced faculty and facilities you would have got if you were in NIT. Being in NIT, you can participate in all the national-level competitions.
• Location: The location of IIIT Bhopal is great. It is located in the peaceful city of Bhopal. It has less traffic and the college is close to both the airport and railway station.
• Hostel: Hostels for the first are at RGPV University, which is the head university of all the engineering colleges in the state. It has a huge campus with modern facilities. Buses are provided from hostel to college and that too free of cost.
• Food: The quality of food at the canteen is not so good.
• Academics: Academics facilities are great and you have to work hard to stay in sync with the syllabus. The course-work will be quite hectic in the first year and you would be given 30,50 or sometimes even 100 questions as an assignment. You will learn C-Programming, HTML, CSS, latex, etc. 

You can also check the latest ranking of the institute to compare. The final decision is yours. 

Both IITD Mechanical as well as IIT BHU CSE are good branches.
IIT BHU is 100 Years old Institution and offers a huge Alumni Network. The course curriculum of CSE is designed in a way that will give you enough Industry exposure. Coding Culture at IIT BHU is also very impressive with 10-12 GSOC Selections every year. The Department Club of Programmers (COPS) conducts Codefest which is the annual Department Fest which witnesses the participation of students and programmers worldwide. Moreover, besides Technical things at IIT BHU you can build up other skills since there are many clubs for Extracurriculars like Aeromodelling Club, Robotics Club, Business Club, Cultural Societies, Film & Media Council, etc. Apart from this, the Life at IIT BHU campus and city life of Varanasi is amazing. The average placement package at this IIT is nearly around 8.19 Lakhs while the Highest was 1.54 Crore in 2019. All the top companies including top tech giants Google, Microsoft, Facebook, Amazon offer jobs as well as other sectors where students get jobs are Consulting, Analytics, Education, Business, etc.

IITD is an old well-reputed IIT. Faculties of the Mechanical Department at IITD are very good and experienced. Also, Peer Group at IITD is very competitive since many top rankers join this college. Mechanical Engineering course curriculum is good and one which provides industry skills. Besides Academics IITD too has many Clubs, Societies where students can join to develop different skills. Also, Campus life of IITD and the City life that Delhi offers is quite amazing. Placements too at IITD are good. In 2019 Mechanical Engineering was the brunch with the highest placement records. Many top Mechanical Core companies visit campus such as HUL, ITC, WIPRO, CBS, HONDA, etc. There are also other job profiles available such as Data Analytics, Software, Consulting, Finance, Education, etc.

You should choose the branch depending on your Interest. Choose Mechanical only if you have keen interest otherwise choose CSE to get more opportunities.